TA903 TMR FreePitch sensor for angle measurement

The TA903 is a FreePitch sensor based on the Tunnel MagnetoResistive (TMR) effect. 

The sensor offers

  • Extremely low harmonic output signals
  • Non-contacting measurement
  • A large working distance
  • High signal amplitudes with simultaneously low offset voltages
  • High stability across the temperature application range

The sensor is a FreePitch sensor, which can be used independently of a magnetic pole pitch.

The sensor design is based on PerfectWave technology which improves the signal quality by suppressing the harmonics.

Suitable for absolute or incremental applications (linear or rotary motion) e.g.:

  • Motor commutation
  • Speed measurement
  • 360° absolute angle detection at the shaft end

Product overview

NameHousingAmplitudeOffsetBridge resistor
TA903ACAChip100 mV/V±3 mV/V10 kΩ
TA903AMALGA6B100 mV/V±3 mV/V10 kΩ

General information

The TA903 consists of two Wheatstone bridges at an angle of 90° to each other. A rotating magnetic field at the sensor level supplies two sine signals with a phase shift of 90° relative to each other with a simple frequency of the magnetic field. As such, the signal information is clear across a 360° rotation of the magnetic field.

The TA903 features PerfectWave technology and delivers extremely low harmonic output signals.

Further application possibilities

TA903 on dipole magnet.

As usual for TMR technology, the FreePitch sensor TA903 also has high signal amplitudes. However, these remain almost constant over a wide field range.

Furthermore, the TA903 convinces with very low offset values (in relation to the signal amplitude).

Without compensation, the sensor already shows a small measurement error of 0.5° with a usable  field of 80 mT. With compensation of amplitude, offset and phase, the measurement error can be reduced to below 0.3°.

Data sheets

Product information

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Design features

Sensitec is increasing the sensor efficiency by means of various design modifications to the chip layout.  The patented solutions, described more closely below, also contribute to better signal quality, reduced sensitivity to stray fields and increased control accuracy. 

FreePitch

FreePitch sensors have been optimized to the extent that they can be used independent of the pole length of the measurement scale. This has the benefit of them being particularly compact and coming very close to a point sensor. They are the ideal choice if a particularly cost-effective solution is needed for the measurement task. In order to keep the dimensions as small as possible, the Wheatstone bridges are nested within each other. In order to generate the sine/cosine signals, both bridges are positioned at an angle of 45° to each other.
FreePitch sensors can be used with pole rings or linear scales with almost any pole length, as well as with dipole magnets.

PerfectWave

The PerfectWave design is applied in order to optimize the signal quality of the FreePitch sensors. The MR strips that serve as resistors have a curved form which is used to filter the harmonics when mapping the magnetic field direction in an electric signal. This filtering is implemented using the special geometry and arrangement of the MR strips and does not cause any additional signal propagation delay. The PerfectWave design is particularly effective for small magnetic fields and results in improved linearity, higher accuracy and better signal quality.